Many controversies over diagnosis arise at postmortem examinations in cases in which renal disease plays the leading or subsidiary rôle in the cause of death. Such disputes arise because of insufficient clinical data, a situation that frequently cannot be avoided because of varied adverse circumstances. However, in the absence of all other data, information concerning only the chemical changes in the blood is frequently of great aid in postmortem diagnosis. Unfortunately, in a good number of cases even this information is not available, and since the pathologist occasionally hesitates to make a diagnosis based entirely on the structural changes of the kidney, the final diagnosis often remains permanently in abeyance.Experiences with several such cases have suggested to us the advisability of making a postmortem examination of the blood in the hope of securing aid in diagnosis in those instances in which the blood was not examined during life. A